1. Field of the Invention
The present invention concerns a rotary plant mowing apparatus used for mowing or cutting grasses, woods and bamboos and, more in particular, it relates to a rotary plant mowing apparatus in which rotary blade units (rotors) are revolved under auto-rotation by a common rotary driving source.
2. Statement of the Related Art
Rotary plant mowing apparatus adapted to cut plants by rotary blade units each having a plurality of cutter units cause a difference of the rotational speed between a central portion and an outer portion if the radius of rotation of the rotary blade units is large, tending to cause uneven mowing near the central portion.
The problem may be overcome by decreasing the radius of the rotary blade unit, but this complicates the operation since the rotary blade unit has to be moved finely in every direction along the ground.
If the rotary blade unit is adapted to revolve under auto-rotation, mowing for a wide range is possible with less movement even if the radius of the rotary blade unit is small. However, such a rotational mechanism requires two driving sources, namely, a driving source for auto-rotation and a driving source for revolution.
Further, in a case where the rotary blade unit is adapted for auto-rotation and revolution by one driving source, when the resistance to the revolution decreases relatively, the auto-rotation speed decreases relatively and no auto-rotation force required for mowing can be obtained. The problem is to be expected.
As another problem, since only one blade edge is provided to one cutter unit, if the blade edge is damaged, the entire cutter unit has to be discarded.
Further, in existent rotary mowers or mowing apparatus, the rotary blade unit is directly coupled to a rotary shaft and joined by inserting a pin between both of the members. Accordingly, if a strong resistance or load exerts on the rotary blade unit, the pin is flexed or the rotary shaft or the motor is overloaded.
Furthermore, in the rotary mower, scattering of rocks or stones can be prevented by attaching a cover to the outside of a rotational trace of the rotary blade unit but attachment of the cover makes it impossible to cut grasses while moving the mower along the ground and mowing can be done only by putting the mower over the ground or grasses.
It is a principal object of the present invention to provide a rotary plant mowing apparatus adapted to revolve a plurality of rotary blade units under auto-rotation by a common rotary driving force, thereby enabling the mowing or cutting operation with no unevenness over a wide range with less movement of the apparatus.
A second object of the present invention is to provide the rotary plant mowing apparatus in which the cutter unit has a plurality of blade edges and a cutting blade edge under use can be replaced with a new one by changing the attaching angle to the rotary blade unit.
A third object of the present invention is to provide the rotary plant mowing apparatus described above of a structure in which a rotary shaft of the rotary blade unit rotates idly upon undergoing a strong resistance to the rotary unit.
A fourth object of the present invention is to provide the rotary plant mowing apparatus having a protection cover on the outside of a revolution trade of the rotary blade unit and capable of mowing or cutting plants while moving the plant mowing apparatus horizontally.
The foregoing objects can be attained in accordance with a rotary plant mowing apparatus of the present invention in which a driven case is engaged rotationally by way of a braking device to a cylindrical frame having a rotary driving shaft pivoted therein, and a plurality of cutter rotary shafts each having a rotary blade unit jointed at a bottom end thereof and being attached to the driven case in parallel with the rotary driving shaft. Rotary bodies, such as pulleys or gears, each having a predetermined circumferential ratio, for example, 3:1, are secured to the rotary driving shaft and the cutter rotary shaft, respectively, and the rotary body for the cutter rotary shaft and the rotary body for the rotary driving shaft are connected by way of a rotation transmitting unit.
The second object can be attained in accordance with a rotary plant mowing apparatus of the present invention in which a plurality of edges are formed on the periphery of the cutter unit of the rotary blade unit and each of the blade edges is turned in the rotational direction for cutting by the change of the attaching angle to the rotary blade unit. The cutter unit of the rotary blade unit may be a flat grade of a saw teeth-like rugged blade.
The third object can be attained in accordance with the rotary plant mowing apparatus of the present invention in which the rotary blade unit and the rotary shaft are engaged under pressure by way of a resilient member.
The fourth object can be attained in accordance with a rotary plant mowing apparatus of the present invention in which a plurality of vertical slits are formed to a side cover of the apparatus.